Hycanthone, lucanthone and niridazole, chemotherapeutic agents in the treatment of schistosomiasis, are attracting wide concern because of their potential carcinogenic and mutagenic hazards to treated individuals in human population. Our studies have shown that hycanthone, lucanthone and their indazole analogs and niridazole are mutagenic in Neurospora crassa. It would be of interest to determine whether hycanthone induces particular types of genetic alterations and whether structurally related compounds cause similar spectra of genetic changes. The genotype and the complementation patterns of each mutant are determined by growing each mutant with each complementation tester. The frequencies of chromosomal deletions are determined by dikaryon and trikaryon tests. Genetic analysis of ad-3 mutants induced by hycanthone and its analogs indicates that these compounds cause similar spectra of genetic alterations in which multilocus deletion is a predominant type.